1. Field of the Invention
The present invention relates to vortex shedding flow measuring devices.
2. Prior Art
In the prior art several patents have illustrated the basic concept of providing an obstacle or body in a fluid flow path which causes vortices to be formed and which vortices set up vibrations or oscillations in the obstacle. Measurement of the vibrations has long been known to provide an indication of the velocity of flow past the obstacle. Devices of the general type are shown in U.S. Pat. No. 3,972,232 wherein a piezoelectric pick-up is used for determining the vibration of the obstacle, and wherein a particular shape of obstacle is provided.
A single bar, flat plate assembly which can be inserted into a conduit is shown in Japanese Utility Model Publication No. 9015/1975. A vortex flowmeter which shows a plurality of bodies arranged in a particular orientation in relation to the direction of flow is shown in Japanese Patent Disclosure No. 20553/1973. Particular attention should be given to FIG. 7(h). The teaching is that a particular spacing relationship is desired between two laterally spaced "pillars" and a downstream pillar to obtain the desired action.
Another type of vortex flowmeter is shown in U.S. Pat. No. 3,796,096.
The use of a bluff body as the vortex shedding obstacle or body is illustrated in U.S. Pat. No. 3,572,117, and probe rods made of a polygonal cross section are disclosed in U.S. Pat. No. 2,813,424. A flowmeter using rectangular vortex shedding probes in one embodiment, wherein the wall of the probe is intended to be the vortex shedding obstacle as well as the moving or sensing element is shown in U.S. Pat. No. 3,927,566.
U.S. Pat. No. 3,948,097 is of interest in that it provides a plurality of slots in a vortex shedding ostacle with the slots arranged to extend transverse to the flow direction, and these slots are alleged to assist in the production and detection of vortices.
Another patent which illustrates three individual flowmeters in a single pipe, is U.S. Pat. No. 3,979,954. Each of the meters generates a separate signal, and the separate signals can be combined to provide an output that is substantially proportional to the flow rate of the fluid.
Investigations of the effects of multiple bars in flow have been made for the purpose of predicting and minimizing structural vibrations in devices such as boiler tubes.